From: Volodymyr Medvid <vmedvid@riseup.net>
To: newlib@sourceware.org
Subject: [PATCH] Fix stdio memory leaks with _REENT_SMALL + _LITE_EXIT
Date: Tue, 12 Apr 2022 16:23:13 +0300 [thread overview]
Message-ID: <20220412132313.39160-1-vmedvid@riseup.net> (raw)
When a thread calls stdio functions (say, printf) and then dies,
_reclaim_reent() runs cleanup_stdio() to free the file buffers
and descriptors created for this thread. This is causing multiple
memory leaks when newlib is configured with _REENT_SMALL
and _LITE_EXIT - this is the standard configuration for
newlib-nano provided with GNU Arm Embedded Toolchain.
1. While __sfp() allocates the FILE objects in GLOBAL_REENT glue chain,
stdio_cleanup walks through the thread-specific glue chain
to run the cleanup_func. Therefore, the FILE objects are never
freed. This leaks ~428 bytes per thread (glue_with_file + 3 x FILE).
To fix this, update __sfp() to use the per-thread glue chain for
stdio descriptors.
2. With _LITE_EXIT enabled, _fflush_r is used as cleanup_func
instead of _fclose_r - as a result, the I/O buffer memory allocated
by __smakebuf_r is never freed - this leaks another 1024 bytes.
To fix this, update cleanup_stdio to always use _fclose_r.
This is a follow-up patch for https://ecos.sourceware.org/ml/newlib/current/017697.html
---
newlib/libc/stdio/findfp.c | 9 ++-------
1 file changed, 2 insertions(+), 7 deletions(-)
diff --git a/newlib/libc/stdio/findfp.c b/newlib/libc/stdio/findfp.c
index 1370b63b8..2799980f3 100644
--- a/newlib/libc/stdio/findfp.c
+++ b/newlib/libc/stdio/findfp.c
@@ -153,7 +153,7 @@ __sfp (struct _reent *d)
if (_GLOBAL_REENT->__cleanup == NULL)
__sinit (_GLOBAL_REENT);
- for (g = &_GLOBAL_REENT->__sglue;; g = g->_next)
+ for (g = &d->__sglue;; g = g->_next)
{
for (fp = g->_iobs, n = g->_niobs; --n >= 0; fp++)
if (fp->_flags == 0)
@@ -209,14 +209,9 @@ cleanup_stdio (struct _reent *ptr)
the aforementioned systems. */
cleanup_func = __sflushw_r;
#else
- /* Otherwise close files and flush read streams, too.
- Note we call flush directly if "--enable-lite-exit" is in effect. */
-#ifdef _LITE_EXIT
- cleanup_func = _fflush_r;
-#else
+ /* Otherwise close files and flush read streams, too. */
cleanup_func = _fclose_r;
#endif
-#endif
#ifdef _REENT_GLOBAL_STDIO_STREAMS
if (ptr->_stdin != &__sf[0])
(*cleanup_func) (ptr, ptr->_stdin);
--
2.25.1
next reply other threads:[~2022-04-12 13:23 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-12 13:23 Volodymyr Medvid [this message]
2022-04-12 16:10 ` Sebastian Huber
2022-04-12 20:57 ` Volodymyr Medvid
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